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Old 24th February 2021, 07:15   #14  |  Link
geometer
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Join Date: Dec 2015
Posts: 59
Quote:
Originally Posted by smel View Post
Here untouched captured video segment with noticeable ringing.
https://drive.google.com/file/d/12eJ...ew?usp=sharing
can you post 5 seconds from the other 2?

what is the correct input statement for reading this apple format?
?? ffmpg(x,y,z,...)

(sorry the only thing I ever do is MPEG2Source () so I have no clue)

it has compression artifacts from the capturing anyway, which adds up to the quagmire.
to process the video in a meaningful way, it will take a lossless capture from the tape.

some simplified theory for the household commonsense:
also, while there are 486/512 lines correctly encoded (so the deinterlace works), the analog corresponding x-dimension is not clear, i.e. how many pixels must the capture have on horizontal scale, to represent an integer number for the width of the ringing? (the ringing artifact must have a distance to the original of precisely 2 or 4 px so what is the dimension of the whole screen in this direction?)
there are known defaults for all types of old video tape formats. hopefully they are truthful to the internal "nyquist/gibb" edge of the device, expressed as a frequency in the analog domain, because this is the root of the ringing. something like 5MHz for a good device, then we must figure out how many cycles of this max f can happen during a cycle of the line scan frequency, then we have to subtract the borders and gaps also, etc. etc. then we know how many pixels this would reflect in the digital domain.
we need to tweak anyway, because of manufacturing differences. the ringing frequency depends on component tolerances.
one more factor, if it is PAL then it has already a digital chopping for the delay line that prepares the color processing. but the actual limit is lower and can influence the ringing frequency.
720 does not look correct to me. perhaps it is something like 640 or even less? you might also take the double value for higher precision. we end up with resizing anyway.

Last edited by geometer; 24th February 2021 at 07:50.
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